Perhaps drinking so much water diluted it (I try to drink 8+ glasses of water a day, and my urine is pretty clear.) But from reading up on pregnancy tests: Any line, whether faint or bold, is a positive.
Make yourself a doc appointment and go get your blood test, hun! Its the only way to be sure, and you will have to do it anyways. I have a feeling that you are, keeping my fingers crossed for you hun!!!